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### Lighting Tab

From the Edit menu, point to Graphic Display Window, and choose Lighting, Materials.

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CAD and Graphic Setup dialog box - Lighting tab

The Lighting tab of the CAD and Graphic Setup dialog box consists of three areas that allow you to define your light sources, your light model, and transparencies.

Light source:

The Light source area defines up to four light sources, each specifying a light direction and color. You can click the Enabled check box and select the appropriate number to create a new light source.

Light source area of the Lighting tab

With the exception of the first light source, which remains always enabled, the Enabled check box lets you turn on or off the current light source.

Once you enable a light source, an active Light direction button becomes selected with a red outline. These buttons define the direction from which the light originates.

The center light direction button acts as if the light comes from the direction you are located as if shining through your computer screen onto the CAD part. The other direction buttons define light coming from other angles.

The Light colors section lets you change the Ambient, Diffuse, or Specular color for the current light source. To change the color, perform the following steps:

1. Click on the colored rectangle beneath each type of light. This action opens the Color dialog box.

2. From the Color dialog box, select the color.

Light source 1 has gray as the default color for Diffuse and Specular, while the other three light sources use black as the default color.

Ambient illumination is light that has been scattered so much by the environment that its direction is impossible to determine - this light seems to come from all directions. Backlight in a room has a large ambient component, since most of the light that reaches your eye has bounced off many surfaces. A spotlight outdoors has a tiny ambient component; most of the light travels is the same direction, and since you are outdoors, very little of the light reaches your eye after bouncing off other objects. When ambient light strikes a surface, it is scattered equally in all directions.

Diffuse light comes from one direction, so it is brighter if it comes squarely down on a surface than if it barely glances off the surface. Once it hits a surface, however, it is scattered equally in all directions, so it appears equally bright, no matter where the eye is located. Any light coming from a particular position or direction probably has a diffuse component.

Specular light comes from a particular direction, and it tends to bounce off the surface in a preferred direction. A laser beam bouncing off a mirror produces almost 100 percent specular reflection. Shiny metal or plastic has a high specular component, and chalk or carpet has almost none. You can think of specular light as "shininess".

If you disable a light source, the Light direction and Light colors features become unavailable for selection.

Light model:

Light model area of the Lighting tab

The Light Model area defines information applied to the entire scene, regardless of the light source.

Two sided lighting – This check box determines whether or not the front and back faces of surfaces should be lighted. You should select this check box for imported IGES files and for some other CAD formats when the surface normals are not correct.

Back face culling – This check box determines whether or not PC-DMIS should cull, or hide, the back faces of surfaces. You should select this check box for IGES files, and some other CAD formats when the surface normals are not correct.

Colormaps - This check box determines whether or not PC-DMIS applies the lighting properties on the Lighting tab to colormaps.

- if you mark this check box, the software applies the lighting properties to colormaps whenever it renders the CAD model.

- If you clear this check box, the software does not apply the lighting properties; the colormap colors have a flat appearance, but the colormap colors exactly match the color scale that the colormap uses.

Ambient – This box defines the ambient color applied to the entire scene. Click on the box to change colors.

Transparency:

Transparency area of the Lighting tab

Working with simulated probes or machines on your screen can be difficult if they block your sight to your part model. To reduce this problem, the Transparency area lets you make certain objects transparent inside the Graphic Display window. In this way, you can see your part model or other CAD objects even if your probe or machine is in the way.

You can make these objects transparent inside the Graphic Display window:

- Part model

- Probe

- Machine

You can also turn on or off the part model's transparency with the Part Model Transparency icon () on the Graphic View toolbar.

Once you have enabled transparency for a simulated machine, you can then select features and other items on your part with a click on your part model through the transparent machine.

Once you select the Enable transparency check box, you can select the other items in the Transparency area. When you enable transparency for an object, the other settings in this area control how the transparency is to be shown.

Single layer - This check box is only enabled when the High quality transparency check box from the OpenGL tab is enabled and checked. If you select the Single layer check box, only the top-most transparent surface of the selected model (CAD Model, Probe, or Machine) is rendered. In effect, this check box hides the internal features of a transparent model even though other models can still be viewed through the transparent model. Note that rendering is faster when this option is selected.

Back face culling - This check box causes PC-DMIS to not draw the back faces of surfaces for the selected transparent object.

Transparency - This slider lets you determine the percentage of transparency for the selected object. Moving the slider to the left makes the display object more opaque, while moving the slider to the right makes it more transparent. The value (0 - 100) can also be updated in the Transparency box to the right of the slider.